1. Field of the Invention
The present invention relates to a composite semiconductor device and, more particularly to, a composite semiconductor device having a power semiconductor element.
2. Description of the Related Art
There is known a power converter as typified by an internal combustion ignition device that drives an inductor load using a switching element. FIG. 13 is a simple circuit diagram of the internal combustion ignition device.
An internal combustion ignition device 100 of FIG. 13 has an ignition coil 101, a switching element 102 connected to the primary side of the ignition coil 101, and a spark plug 103 connected to the secondary side of the ignition coil 101. When an ignition signal is input to a terminal 104 of the switching element 102, primary current is made intermittent to induce high tension current to the secondary side of the ignition coil 101, and the spark plug 103 converts the high tension current into a spark for ignition.
As the switching element used in the internal combustion ignition device, a thyristor, a GTO (Gate Turn-Off thyristor), or the like has been generally used. However, the switching time of such a switching element is several microseconds, the current change rate thereof is comparatively low, and the surge voltage thereof is comparatively small.
In recent years, a voltage drive type high-speed switching element that operates with a switching time shorter than that of the thyristor or GTO, such as an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (MOS Field Effect Transistor) has come to be used as the abovementioned switching element 102 and applied in various fields.
The above high-speed switching element performs high-speed switching operation with a switching time one order of magnitude shorter than the thyristor or GTO. Accordingly, the current change rate of a main circuit (circuit connected to the primary side of the ignition coil 101) and the surge voltage also becomes considerably large unless the inductance of the main circuit is reduced significantly. When the surge voltage becomes considerably large, voltage exceeding rated voltage is applied to the high-speed switching element itself, which may result in destruction due to overvoltage. This further may induce large noise to adversely affect peripheral devices. Further, the current interruption speed of the switching element on the primary side of the mutual inductance circuit (ignition coil 101) is too high, so that electromotive voltage is generated due to a parasitic inductance on the primary side, which may cause malfunction of other electric circuits.
Under such circumstances, Patent Document 1 discloses a power converter that increases the speed of the switching operation of a high-speed switching element to suppress the current change rate at the switching operation time, to reduce a switching loss, to suppress surge voltage and to reduce noise given to an external apparatus.
In Patent Document 1, a voltage command correction means using a capacitor and a resistor is provided so as to suppress the voltage change rate and current change rate at the OFF-time of the switching element. Further, Patent Document 1 discloses that the switching element and voltage command correction means are housed in a single package.